This invention relates to a pressure-fluid-operable vehicle brake system which is fed by an auxiliary energy supply system and including a master cylinder device in which a booster piston is slidably disposed.
In such known vehicle brake systems, the booster piston comprises an effective area for the pressurization of a wheel brake cylinder which area remains unchanged in the event of failure of the auxiliary energy supply system. It is a disadvantage that a very high force must be applied on the brake pedal in order to obtain the required deacceleration when the auxiliary energy supply system has failed.
It is a object of the present invention to improve upon a pressure-fluid-operable vehicle brake system of the type initially referred to such that the required deacceleration is reliably attained or exceeded by the application of lower force on the brake pedal.